1. Field of the Invention
The present invention concerns the measurement of intramuscular fat, i.e., marbling, in cattle using ultrasound to produce an image of an interior portion of a muscle and then to analyze data representative of that image to produce a measurement of marbling.
2. Description of the Prior Art
The grading systems for beef carcasses emphasize leanness in terms of yield grades and palatability in terms of quality grades, ice. intramuscular fat or marbling. Marbling is considered an indicator of favorable ogano-leptic properties such as juiciness, flavor and tenderness. The yield and quality grades of beef are determined after slaughter. If these grades could be determined accurately in live cattle, producers would have the ability to cluster live cattle during the feedlot phases on the basis of anticipated grades to satisfy packer and consumer specifications. Additionally, this would enable cattle breeders to select breeding stock on the basis of the desirable grading traits.
Ultrasound techniques have been used with some success for determining anticipated yield grades in cattle. A smooth tissue boundary such as that between subcutaneous fat and muscle results in a specular reflection of the ultrasound that produces a congruent image on the ultrasound monitor. Because of this, ultrasound produces a fairly accurate image of backfat and other attributes predictive of yield grade.
The ultrasound techniques have not been successful, however, in producing images representative of marbling. This is because the intramuscular fat deposits of varying sizes and shapes present discontinuities that cause sound waves to scatter rather than echo back to the ultrasound probe. This scattering causes constructive and destructive interference at the probe in a manner analogous to acoustical noise and produces a graininess or mottling in the ultrasound images known as "speckle." Additionally, as marbling increases, the degree of scatter increases.
In the prior art, various attempts have been made to use the speckle itself as an indicator of marbling. For example, in one prior art technique, the speckle in ultrasound images is analyzed visually. With sufficient experience and training, this technique has provided encouraging results, but requires subjective judgment by an individual; subjective judgment in the grading of beef has been a problem in the prior art because it leads to inconsistent results over time and from individual to individual.